The present invention relates generally to controlling one or more system parameters and, more particularly, to methods for flow calibration of transient systems.
Industrial systems that control various system parameters (e.g. pressure, flow rate, temperature, and the like) often encounter various system disturbances. In order to maintain the system within established parameters, the control scheme for the system is designed to respond to environmental changes and variable properties of fluids or materials contained within the system. Such control systems often detect and counteract gradual changes in the system through monitoring parameters critical to system performance.
Some industrial systems utilize sprayers to dispense material (e.g. paint, adhesive, epoxy, and the like) at a specific pressure and flow rate. In systems that operate continuously or for relatively long periods of time at a single pressure and flow rate, the pressure and flow rate reach steady state. Thus, minor changes in the material and/or system performance can be carefully monitored and counteracted by a conventional control scheme.
However, when such systems operate at multiple pressure and flow rate combinations in which some conditions operate for relatively short durations, the pressure and flow rate do not reach steady state. Pressure and flow rate changes and/or fluctuations during transient periods within the system are problematic for control systems because conditions are different at the sprayer outlet than at measurement locations with the system. Failing to account for these transient conditions can result in over-dispensing or under-dispensing material.
In some traditional control schemes, transient periods are controlled by segregating system operating conditions and performing a calibration routine prior to performing each operation. However, calibration routines increase manufacturing costs and disrupt manufacturing work flow because production pauses during the calibration routine. In other traditional control schemes, transient periods are controlled by dispensing excess material until the system reaches steady state. Once the system is at steady state, the traditional control scheme is capable of accounting for minor disturbances. However, dispensing excess material increases material costs.
Therefore, a need exists for controlling the pressure and flow rate of an industrial system that can cost-effectively adapt to multiple operating conditions, environmental changes, and transient conditions.